Telephone system



Oct. 23, 1923. 1,471,639

D. F. WHITING TELEPHONE SYSTEM Filed July 22 1919 I //1 van for Dona/d E Wfl/f/ng Patented Oct, 23, @2351 outrun stares PATEN'E OFFICE DONALDF. WHITING, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC 003.7.- PANY, INCORPORATE, OF NEW YORK, N. Y., A CORPORATION 015' NEW YORK TELEPHONE SYSTW.

Application filed @1322,

To all whom it may concern:

Be it known that 1, Donnie F. WHIrING, a citizen of the United States, residing in New York, in the county of Bronx and 5 State of New York, have invented certain new and useful Improvements in Telephone Systems, of whichthe following is a full, clear, concise,'and exact description.

'Ehis invention relates to telephone sys w tems and more particularly to a system'provided with attenuation equalizing means for the voice frequency range so that it will transmit voice currents without serious distortion and at the same time will transmit ringing currents or other signaling currents without having their strength reduced by the action of the attenuation equalizer.

The transmission through a telephone line generally varies in efiiciency with the different frequencies. A line usually transmits the lower voice frequencies more efii- I ciently than the higher voice frequencies. This is true even when the line is provided 1 with loading coils and repeaters with asso ciatedtransformers. It has been proposed heretofore to place in shunt to such a line at a suitable point an impedance or network of impedances which will discriminate against the lower voice frequencies byacting as a short circuit therefor to the desired extent. An equalizer of this type which is designed so that it will secure a total transmission of voice currents substantially without distortion is fully described in the patent to Ray S. Hoyt, No. 1.453380, granted May 1, 1923. An attenuation equalizer may bedefined as a device adapted to be connected to a lineand having an attenuation which is complemental to the attenuation caused by the line over a range of frequencies.

Ringing or other signaling currents are however, of such low frequency that they are very inefiiciently transmitted bythe. repeaters and associated transformers. When, therefore, they are sent over a line having a shunt equalizer of the above type, they would be materially reduced in amplitude if the equalizer were permitted to function in its normal manner. It is the object of this invention to provide means for effectively preventing the shunt equalizer from carrying currents of a particu 1919. Serial No. 312,641.

that of the ringing The invention will be more fully understood from the following detailed descript1on and claims taken in connection with the accompanying drawings in which Fig.

1 is a portion of a circuit'showing the invention placed directly between line wires, and Fig.2 is a similar view showing the invention applied to a vacuum tube repeater.

Referring to the drawings by reference numerals, the line 'wires -10.and 11 form part of a line, the unequal attenuating effect of which it is desired to equalize. The

equalizer 12 is shown in. the drawings ashaving parallel inductance and capacity,

indicated at 13 and 14, respectively; This,

however, is for the purpose of illustration only, and it is to be understood that the equalizer will consist of such an arrangement of inductance, capacity, or resistance or combinations thereof as may be required by the transmission characteristics of the particular line with which it is to be used. In general, the impedance of the equalizer .will be high for the higher frequencies in the voice range and relatively low for the lower frequencies." 0,

In series with the equalizer 12 1s a network 15 comprising parallel inductance and capacity 16 and respectively. These form a circuit which is tuned a0c01d11 1'g to the formula: a

f 21 /LC' l to the frequenc of "the signaling current employed on t e line. This renders the shunt path containing the attenuation equalizer anti-resonant to the signaling currents, and since the tuned circuit 15 contains very little resistance it operates substantially to open the shunt ath by offering a very high impedance w enever signaling infinity, the formula for timing isas fol lows? 4 ia E7211? Some resistance may be desirable in the tuned circuit, when it isjdesired to render its impedance high to a band of frequencies rather than to a single frequency. Such resistance may be incorporated in the inductance coil 16 or may be-separate therefrom.

In Fig. 2 the line comprising wires 10 and 11 is inductively coupled to a vacuum tube repeater 18. The transformer 19 with midpoint connection 20 is employed for convenience in phantoming the line. Across the primary of the input transformer 21 is connected the potentiometer 22 for control ling the amplification of repeater 18. The

attenuation equalizer 12 and tuned circuit 15 are placed in series with potentiometer 22, where they function 'just as described above in connection with Fig. 1.

. While two embodiments of the invention have been illustrated and described, it is to be understoodthat the invention is not limited to the forms shown but includes equivalentmeans for accomplishing its object within the scope of the appended claims.

What is claimed is:

.1. In combination,'a telephone circuit, and a shunt path, the impedance of a portion of which is relatively high for one range of frequencies to, be transmitted and relatively low for another range of frequencies to be transmitted, the impedance of another portion of said shunt path for a particular group of frequencies within said second mentioned range being very high as compared with its impedance for other frequencies to be transmitted, said two portions being in series with each other.

2. In combination, a telephone circuit, and a shunt path, the impedance of a portion of which is relatively high for one range of frequencies to be transmitted and relatively low for another range of frequencies tobejtransmitted, the impedance of another portion of said shunt path for a particular frequency wi'thin said second mentioned range bemgvery high as compared with its impedance for other frequencies to be transmitted, said two portions being in 's'eries viiith each other.

3. In combination, a telephone circuit, an

attenuation equalizer in shunt to said cir cuit,'-an-d a tuned circuit interposed between said equalizer and one side of 'said circuit- 4.'In.combination, a telephone circuit, an

attenuation equalizer in a path in shunt to said. circuit and anetwork-comprising parallel. inductance and capacity in said path in series with said equalizer, said network being tuned to the frequency of signaling currents sent out on said circuit.

5. In combination, a telephone circuit, the attenuation of which is greater for high frequencies than for low frequencies, an equalizer.network in shunt to said circuit and adapted to short-circuit low frequencies to a greater extent than high frequencies, and

means to render said shunt anti-resonant to a particular lowfrequency.

6. In combination, a line, a repeater, a transformer couplin said line to the input of said repeater, an a potentiometer shunt connected across one winding of-said transformer, said shunt comprising a variable resistance, a network adapted to equalize the transmission of voice currents, and a tuned circuit to render said shunt anti-resonant to a signaling current frequency.

7. In combination, a line, a repeater, a

transformer. between said line and the input of said repeater, and a potentiometer shunt connected across the primary of said transformer, said shunt comprising a variable resistance, a network adapted to equalize the transmission of voice currents, and a tuned circuit to render said shunt anti-resonant to a signaling current frequency.

8. In combination, a repeater for alternating currents, a potentiometer effectively in shunt to said repeater, and an anti-resonant circuit in the shunt path comprising said potentiometer, said circuit being tuned to a frequency which is to be; transmitted by said repeater with maximum efficiency.

9. In combination, a line, a voltage operated device connected thereto, a path cont-aining resistance bridged across said line. and an anti-resonant circuit in said path to impede the passage of a frequency which is to I be transmitted by said repeater with maximum efiiciency.

I 10. In combination, a telephone line, a re peater, a transformer between said line and said repeater, a path comprising resistance DONALD F. WHITING. 

